It's not easy to drown out Trump. But at his rival rally Monday night, O'Rourke showed he was willing to go to great lengths to try. The event was the latest signal that the former Democratic congressman is readying for a White House run, and it was a window into what an O'Rourke campaign might look like.

On a makeshift stage at a baseball field, O'Rourke aimed for optimism and placed his opposition to Trump's immigration policies front and center. He wants to stick to "what unites us rather than what divides us," O'Rourke said, reviving the rhetoric that made him a Democratic star during his failed Texas Senate bid last year. He sprinkled in fluent Spanish and praise for immigrants and was backed by a Mariachi band. Celebrity photographer Annie Leibovitz was spotted backstage, following O'Rourke closely, and has been taking his picture around El Paso in recent weeks.

O'Rourke decided to stage a counter-rally after Trump announced plans to stump in El Paso. The president has used this city to make his case for a wall along the U.S.-Mexico border. O'Rourke told reporters Monday he "just wasn't going to let anyone else tell El Paso's story."

The move was characteristically unconventional and media savvy. At a time when many in the Democratic field are keeping Trump at arm's length, O'Rourke went head-to-head, leading a march that hugged part of El Paso's border with Mexico before concluding at the baseball complex close to where Trump was delivering his own speech at the same time.

The march followed the border for a few blocks, affording views of the towering metal slats erected along it. Wearing a black fleece over a white button-up shirt with the sleeves rolled up that has become a trademark, O'Rourke grinned widely and waved at longtime supporters and friends, stopping frequently to hug many of them. Marchers all around him alternated between chanting "No wall!" and "Beto! Beto! Beto!"

It was a clear return to the arena for a politician who has recently made headlines for his public soul-searching and road-tripping, both documented in social media posts and online essays. In an interview with Oprah Winfrey last week, he acknowledged he had been coming to terms with his November loss to Republican Sen. Ted Cruz and was now considering a presidential bid.

The president says "Walls work," arguing that El Paso has become one of the safest cities in the nation because of border barriers standing between it and Ciudad Juarez, Mexico, just across the Rio Grande.

Fencing has been around in some form here since the 1970s, though it wasn't really fortified until after 2006. But FBI statistics show El Paso had very low crime rates per capita years before the border barriers were reinforced -- and O'Rourke says walls have nothing to do with keeping the city safe.

"We know that walls do not save lives. Walls end lives," he told the ballfield rally crowd. "We stand for America, and we stand against walls."

It was the first of what will be many dueling campaign rallies of the 2020 presidential cycle -- and turnout was strong despite cold, blustery conditions that were unusual in a West Texas locale known for its desert heat. O'Rourke's camp said 7,000 people crowded onto an open-air baseball diamond. Trump filled a nearby coliseum that could similarly hold thousands.

Claiming that his rally drew 35,000 attendees including those listening outside, the president also initially, falsely said only 200 to 300 were at O'Rourke's rally. "That maybe ends his presidential challenge," Trump said.

At a Cabinet meeting back in Washington on Tuesday, Trump was still raising the issue, saying, "We had a competitor that decided to challenge me with the crowds and he failed very badly."